Structures utilizing a structured magnetic material and methods for making

ABSTRACT

A motor comprises a stator comprising at least one core; a coil wound on the at least one core of the stator; a rotor having a rotor pole and being rotatably mounted relative to the stator; and at least one magnet disposed between the rotor and the stator. The at least one core comprises a composite material defined by iron-containing particles having an alumina layer disposed thereon.

CROSS REFERENCE TO RELATED APPLICATIONS

This application claims the benefits of Provisional Patent ApplicationNo. 61/884,415 filed Sep. 30, 2013; Provisional Patent Application No.61/920,043 filed Dec. 23, 2013; Provisional Patent Application No.61/933,386 filed Jan. 30, 2014; and Provisional Patent Application No.61/941,644 filed Feb. 19, 2014, the contents of which are herebyincorporated by reference in their entireties.

GOVERNMENT SUPPORT

This invention was made with Government support under SBIR Phase IXGrant Number 1230458 awarded by the National Science Foundation. TheGovernment has certain rights in this invention.

BACKGROUND

Technical Field

The exemplary and non-limiting embodiments disclosed herein relategenerally to magnetic materials and structures incorporating suchmaterials and, more particularly, to soft magnetic materials havingproperties favorable for use in energy efficient devices.

Brief Description of Prior Developments

Automated mechanical devices generally use electric motors to providetranslational or rotational motion to the various moving elements of thedevices. The electric motors used typically comprise rotating elementsassembled with stationary elements. Magnets are located between therotating and stationary elements. Coils are wound around soft iron coreson the stationary elements and are located proximate the magnets.

In operating an electric motor, an electric current is passed throughthe coils, and a magnetic field is generated, which acts upon themagnets. When the magnetic field acts upon the magnets, one side of therotating element is pushed and an opposing side of the rotating elementis pulled, which thereby causes the rotating element to rotate relativeto the stationary element. Efficiency of the rotation is based at leastin part on the characteristics of the materials used in the fabricationof the electric motor.

SUMMARY

The following summary is merely intended to be exemplary and is notintended to limit the scope of the claims.

In accordance with one aspect, one example of a motor comprises a statorcomprising at least one core; a coil wound on the at least one core ofthe stator; a rotor having a rotor pole and being rotatably mountedrelative to the stator; and at least one magnet disposed between therotor and the stator. The at least one core comprises a compositematerial defined by iron-containing particles having an alumina layerdisposed thereon.

In accordance with another aspect, another example of a motor comprisesa slotless stator comprising at least one core formed of a soft magneticcomposite material and coils disposed on the at least one core; a rotorrotatably mounted relative to the slotless stator; and at least onemagnet mounted on the rotor between the rotor and the slotless stator.The soft magnetic composite material comprises particles of aniron-aluminum alloy having insulating outer surfaces comprising alumina.

In accordance with another aspect, an example of a slotless flux motorcomprises a stator defined by a continuous surface at which at least onecore is disposed and a winding disposed on the at least one core; arotor having a rotor pole and being rotatably mounted in the stator; andat least one magnet mounted between the stator and the rotor pole. Aconical air gap is defined between the stator and the at least onemagnet, wherein the conical air gap allows flux flow along radial,axial, and circumferential directions of the motor. The at least onecore comprises a soft magnetic composite material defined by ironparticles encapsulated in alumina.

BRIEF DESCRIPTION OF THE DRAWINGS

The foregoing aspects and other features are explained in the followingdescription, taken in connection with the accompanying drawings,wherein:

FIG. 1 is a schematic representation of one exemplary embodiment of asoft magnetic material having an aggregate microstructure of permeablemicro-domains separated by insulation boundaries;

FIGS. 2A and 2B are schematic representations of a deposition process ofan iron-aluminum alloy to form the soft magnetic material of FIG. 1;

FIGS. 3A through 3C are photographs of the microstructure of the softmagnetic material produced using various deposition techniques;

FIGS. 4A through 4C are photographs of structures fabricated using thesoft magnetic material;

FIGS. 5A through 5D are schematic representations of variousmorphologies of the soft magnetic material;

FIG. 6A is a schematic representation of a ring structure fabricatedusing the soft magnetic material;

FIGS. 6B through 6D are photographs of the microstructure of the softmagnetic material illustrating isotropic characteristics in the XZ, YZ,and XY planes;

FIG. 7 is a perspective sectional view of one exemplary embodiment of amotor incorporating the soft magnetic material;

FIG. 8 is a perspective sectional view of another exemplary embodimentof a motor incorporating the soft magnetic material;

FIG. 9 is a perspective sectional view of another exemplary embodimentof a motor incorporating the soft magnetic material;

FIG. 10A is a perspective sectional view of another exemplary embodimentof a motor incorporating the soft magnetic material;

FIG. 10B is a perspective view of one exemplary embodiment of a statorpole of the motor of FIG. 10A;

FIGS. 11 through 14A are perspective sectional views of other exemplaryembodiments of a motor incorporating the soft magnetic material;

FIG. 14B is an exploded perspective sectional view of the motor of FIG.14A;

FIG. 15A is a perspective sectional view of another exemplary embodimentof a motor incorporating the soft magnetic material;

FIG. 15B is an exploded perspective sectional view of the motor of FIG.15A;

FIG. 16A is a perspective sectional view of another exemplary embodimentof a motor incorporating the soft magnetic material;

FIG. 16B is an exploded perspective sectional view of the motor of FIG.16A;

FIG. 17A is a schematic representation of a stator cross section of oneexemplary embodiment of a motor;

FIGS. 17B and 17C are schematic representations of stator cross sectionsof exemplary embodiments of motors incorporating the soft magneticmaterial;

FIG. 18A is a perspective sectional view of another exemplary embodimentof a motor incorporating the soft magnetic material;

FIG. 18B is a schematic representation of a top view of a tapered statorpole of the motor of FIG. 18A;

FIG. 18C is an exploded perspective sectional view of the motor of FIG.18A;

FIG. 19 is a schematic representation of a section of a motorincorporating the soft magnetic material;

FIG. 20 is a perspective sectional view of an exemplary embodiment of astator of a motor incorporating the soft magnetic material;

FIG. 21 is a perspective sectional view of an exemplary embodiment of arotor for use with the stator of FIG. 20;

FIGS. 22 and 23 are perspective sectional views of exemplary embodimentsof motors incorporating the soft magnetic material;

FIG. 24 is a perspective sectional view of an exemplary embodiment of arotor of a motor incorporating the soft magnetic material;

FIG. 25 is a perspective sectional view of an exemplary embodiment of astator for use with the rotor of FIG. 24;

FIG. 26 is a perspective sectional view of an assembly of the rotor andstator of FIGS. 24 and 25, respectively;

FIG. 27 is a schematic representation of a cross section of an exemplaryembodiment of a stator incorporating the soft magnetic material;

FIGS. 28 and 29 are perspective sectional views of exemplary embodimentsof motors incorporating the soft magnetic material;

FIG. 30 is a perspective sectional view of one exemplary embodiment of aslotless stator incorporating the soft magnetic material;

FIG. 31 is an exploded perspective sectional view of one exemplaryembodiment of a rotor for use with the slotless stator of FIG. 30;

FIG. 32 is a perspective sectional view of one exemplary embodiment of amotor incorporating the slotless stator and the rotor of FIGS. 30 and31, respectively;

FIG. 33 is a perspective sectional view of another exemplary embodimentof a motor incorporating a slotless stator and the soft magneticmaterial;

FIG. 34 is a perspective sectional view of one exemplary embodiment of ahybrid slotless motor;

FIGS. 35A through 35C are perspective views of a stator of the motor ofFIG. 34;

FIGS. 35D and 38 are perspective views of a coil winding of the motor ofFIG. 34;

FIG. 35E is a perspective view of a stator core of the motor of FIG. 34;

FIGS. 36A through 36E are perspective and perspective sectional views ofa rotor of the motor of FIG. 34;

FIG. 37 is a schematic representation of the motor of FIG. 34;

FIG. 39 is a side sectional view of a rotor pole of the motor of FIG.34;

FIG. 40 is a schematic, representation of the motor of FIG. 34 showingcoil windings potted onto the stator;

FIG. 41 is an electron microscope image of a cross section of the softmagnetic material;

FIG. 42 is a graphical representation of an X-ray diffraction spectrumof the soft magnetic material;

FIG. 43 is an image of a microstructure of sprayed particles of anickel-aluminum alloy;

FIGS. 44A and 44B are phase diagrams of Fe—Al—Si alloy and Fe—Al alloy,respectively;

FIG. 45 is a schematic representation of a mask and stencil system usedto form a stator incorporating the soft magnetic material;

FIGS. 46A through 46C are schematic representations of an exemplaryembodiment of a motor having a slotted stator.

DETAILED DESCRIPTION OF EMBODIMENTS

Referring to FIGS. 1 through 6D, exemplary embodiments of a softmagnetic material for electrical devices and components of electricaldevices, as well as methods of making such materials and the electricaldevices themselves, are disclosed. The soft magnetic material isdesignated generally by the reference number 10. Electrical devices withwhich such soft magnetic material 10 may be used include, but are notlimited to, electric motors. Such electric motors may be used, forexample, in robotic applications, industrial automation, HVAC systems,appliances, medical devices, and military and space explorationapplications. Components with which such material may be used include,but are not limited to, electric motor winding cores or other suitablesoft magnetic cores. Although the present invention will be describedwith reference to the embodiments shown in the drawings, it should beunderstood that the present invention may be embodied in many forms ofalternative embodiments. In addition, any suitable size, shape, or typeof materials or elements could be used.

Referring specifically to FIG. 1, the soft magnetic material 10 has amicrostructure of suitable softness and mechanical strength and isformed as a bulk material via deposition of an alloying element in areactive atmosphere to produce an aggregate of small micro-domains 12 ofhigh permeability and low coercivity separated by insulation boundaries14 that limit electrical conductivity between the micro-domains 12. Useof such bulk material in electrical devices allows for gains inperformance and efficiency. For example, use of the soft magneticmaterial 10 in motor winding cores may provide an efficient magneticpath while minimizing losses associated with eddy currents induced inthe winding cores due to rapid changes of magnetic fields as a motor inwhich the motor winding cores are mounted rotates. This allows for thesubstantial elimination of design constraints generally associated withthe anisotropic laminated cores of conventional motors.

Referring to FIGS. 2A and 2B, a schematic representation of oneexemplary embodiment of a deposition process to obtain the soft magneticmaterial 10 is designated generally by the reference number 20 and ishereinafter referred to as “deposition process 20.” As shown in FIG. 2Aof the deposition process 20, a particle 22 of the alloying element isdeposited onto a substrate 24 using a single-step net-shape fabricationprocess based on metal spray techniques. To obtain the resulting softmagnetic material 10 as having the desired microstructure, variousparameters pertaining to the state of alloy used are defined. Withregard to a first exemplary parameter, the temperature of the particle22 is sufficiently high enough to soften the material of the particle 22while being below the melting point of the material. Thus, the particle22 remains substantially a solid and maintains its overall aspect ratioupon impacting the surface of the substrate 24. More specifically, theparticle 22 is in a semi-molten state while in flight. With regard to asecond exemplary parameter, oxidation of the particle 22 is limitedduring the deposition process 20, which allows it to remainsubstantially metallic and to retain its mechanical strength andmagnetic properties. With regard to a third parameter, the velocity ofthe particle 22 during the deposition process 20 may meet or exceed someminimum in-flight velocity that ensures adhesion of the particle 22 withpreviously deposited particles, thereby allowing for the buildup of abulk of alloy to form the soft magnetic material 10 with sufficientmechanical strength, as shown in FIG. 2B. The foregoing parameters (aswell as other parameters) may be met through the selection of a particlesize range, chemical composition, and various process parameters of thedeposition process 20. A system used to carry out the deposition process20 may be a High Velocity Air Fuel (HVAF) system, a High VelocityOxy-Fuel (HVOF) system, or a plasma spray system.

Commercially available alloying elements may be used as the particles22. For example, the alloying element may be any suitable aluminum-basedpowder (e.g., FE-125-27, or the like), such as those available fromPraxair Surface Technologies of Indianapolis, Ind. In one exemplaryembodiment, the alloy may have a composition of 89% Fe-10% Al-0.25% C(all percentages being weight percent). Such an alloy has a meltingpoint of about 1450 degrees C. and is suited to use in HVAF systems inwhich a carrier gas used to gas-atomize the alloy has a temperature ofabout 900 degrees C. to about 1200 degrees C. Such alloy is also suitedfor HVOF systems that operate at temperatures below about 1400 degreesC. Although the exemplary embodiments described herein are directed toan alloy having a composition of 89% Fe-10% Al-0.25% C, alloys of othercompositions may be employed in other exemplary embodiments.

The alloy particles are generally spherical and capable of beinggas-atomized, which renders them suitable for use as the particles 22 inthe HVAF or HVOF systems as they can flow freely without formingclusters during the deposition process 20. Selection of the size of thealloy particles influences the particle velocity as well as thetemperature of the alloy particles during the deposition process 20. Inone exemplary embodiment using deposition via HVOF, alloy particles inthe range of about 25 microns to about 45 microns may yield the desiredparticle temperatures and velocities.

In the deposition process 20 using the HVAF system, the desiredmicrostructure of the resulting soft magnetic material 10 may beproduced as a bulk material by deposition of successive thin coatings.The HVAF system may use a focused particle beam and may have adeposition efficiency of about 80% or more. As shown in FIG. 3A, across-section of the microstructure of the soft magnetic material 10illustrates the distinct micro-domains 12, where larger particles of thesoft magnetic material 10 maintain their overall aspect ratio and aremarked by the distinct boundaries 14.

The deposition process 20 using the HVOF system may operate in atemperature range of about 1400 degrees C. to about 1600 degrees C. toproduce the desired microstructure of the soft magnetic material 10 asshown in FIG. 3B. In the HVOF system, the soft magnetic material 10 maybe produced using a low combustion temperature setting to providedeposited material as a thin coating. However, this low combustiontemperature setting may be accompanied by lower velocities of theparticles 22 impacting the substrate 24, thereby resulting in depositionefficiencies of less than 50%.

Referring to FIG. 3C, the desired microstructure of the soft magneticmaterial 10 may be produced using a low-energy plasma spray system. Ascan be seen, the distinction between the micro-domains 12 and largerparticles may not be as readily discernible as in soft magneticmaterials 10 produced using HVAF or HVOF systems.

In the deposition process 20 using any of the foregoing exemplarysystems, the soft magnetic material 10 is formed by the thermal sprayingof the alloy as particles 22 on the substrate 24. The sprayed particles22 form a dense, closely-packed solid layer of material that iscomprised of the densely-packed micro-domains 12 separated by theelectrically insulating insulation boundaries 14. Furthermore, thesprayed particles 22 forming the solid layer of material may be subjectto heat treatment at a temperature of about 1925 degrees F. for about 4hours, then slow cooled to about 900 degrees F. (at a rate of about 100F degrees per hour for about 10 hours), then further air cooled to aboutroom temperature.

The alloying element may be defined by particles 22 having any ofseveral various morphologies. In any morphology, the alloying element(impacting particles) comprises iron and aluminum, of which the aluminumoxidizes to form a protective layer of alumina (i.e., aluminum oxide) onthe iron. The protective layer of alumina may completely surround theparticle core, or the particle core may be less than fully covered dueto the presence of imperfections or occlusions in the protective layer.Because alumina is more stable than any oxide of iron, a suitableconcentration of aluminum in the alloy provides for sufficient amountsof alumina with no (or substantially no) iron oxide. In one exampleembodiment, the alloy is an Fe—Al alloy comprising 89% Fe-10% Al-0.25%C. The alloy is not limited in this regard, as any other suitablematerial may be used.

Referring to FIGS. 4A through 4C, using the deposition process 20, thesoft magnetic material 10 may be used to produce ingots 30 (FIG. 4A),cylinders 32 (FIG. 4B), or any suitable structure that can be machinedto produce ring-shaped parts 34 (FIG. 4C). The structures produced inthe deposition process 20 (e.g., the cylinders 32, the ring-shapedparts, and the like) may be used as elements in the fabrication ofmotors and motor components.

In one exemplary morphology of the particle 22 used to form the softmagnetic material 10, as shown in FIG. 5A, the particle 22 has a uniformcomposition of Fe—Al alloy 40. Aluminum at the surface of the particle22 reacts with the oxygen in the surrounding environment (which may beair or oxygen-enriched air) to form alumina, thus resulting in a Fe—Alalloy particle with a thin alumina layer 42 on an outer surface thereof.The aluminum concentration of the Fe—Al alloy 40 is selected tofacilitate formation of a continuous alumina layer 42 while eliminatingor at least minimizing the formation of iron-oxide. Because the rate ofoxidation increases with temperature, the particles may be at anelevated temperature to increase the oxidation kinetics. Particletemperature is also raised to a sufficiently high temperature to softenit and to enable deformation necessary to form a densely packedstructure. In order to form a densely packed solid, particles areaccelerated to a sufficient speed prior to hitting the surface. In someembodiments, silicon may be added as an alloying element. In somecompositions, silicon will improve magnetic properties and at the sametime not impede the formation of alumina.

In another exemplary morphology of the particle 22 as shown in FIG. 5B,the particle 22 may be defined by a concentration gradient from theFe—Al alloy 40 to the surface. Aluminum at the surface is formed bysuitable concentrations of aluminum in the Fe—Al alloy. However,aluminum decreases the saturation flux density of iron. To maximizesaturation flux density, the resulting particles have a pure iron core44 and an increasing concentration 46 of aluminum from the iron core 44to the particle surface 48. This morphology is achieved by deposition ofa layer of aluminum on the particle and heat treatment to allow aluminumto diffuse into the particle to form an alloy with the varyingconcentration 46 of aluminum. The particles are heat treated in an inertenvironment to prevent oxidation of aluminum with the aluminumconcentration being selected to facilitate the formation of thecontinuous alumina layer 42 along the surface 48 without (or at leastsubstantially without) formation of iron oxide. The surroundingenvironment may be air or oxygen-enriched air, and since the rate ofoxidation increases with temperature, the alloy particles may be at anelevated temperature to increase the oxidation kinetics. As with theprevious embodiment, in order to form a densely packed solid, particlesare accelerated to a sufficient speed prior to impacting the surface.Particle temperature is also raised to a sufficiently high temperatureto soften the alloy material and to enable deformation necessary to forma densely packed structure. Furthermore, silicon may be added as analloying element to, for example, improve magnetic properties while notimpeding the formation of alumina.

In another exemplary morphology of the particle 22 as shown in FIG. 5C,a base particle 50 of iron or an iron alloy may be encapsulated in thealumina layer 42. These alumina-coated iron (or iron alloy) particlesmay be obtained through an atomic layer deposition (ALD) process, whichinvolves depositing a thin layer of aluminum and exposing the layer tooxygen to allow the layer to oxidize, then successively depositing andoxidizing subsequent layers. Deposition processes are not limited toALD, however, as any suitable process may be provided to form thealumina layer on the iron or iron alloy particles. Several such layersare deposited to arrive at the required thickness of the alumina layer42. The base particle 50 could be pure iron or an alloy of iron thatenhances magnetic properties, such as iron-cobalt, iron-nickel,iron-silicon, or the like. In order to form a densely packed solid,particles are accelerated to a sufficient speed prior to hitting thesurface. During the deposition process 20, particle temperature israised to a sufficiently high temperature to soften the particles and toenable deformation of the particles to form a densely packed structure.As with other embodiments, silicon may also be added as an alloyingelement to improve magnetic properties while avoiding or minimizing theformation of alumina. The addition of 1% silicon as an alloying elementto the Fe—Al alloy having about 10 wt. % aluminum allows for theproduction of raw material with minimal carbon content (and possiblylarger-sized particles).

In another exemplary morphology of the particle 22 as shown in FIG. 5D,the base particle 50 comprises an iron or an iron alloy core that may beencapsulated in aluminum, which oxides to form the alumina layer 42during the deposition process. The base particle 50 is, for example,pure iron or an alloy of iron that enhances magnetic properties (e.g.,iron-cobalt, iron-nickel, iron-silicon, or the like). The surroundingenvironment may be air or oxygen-enriched air or an environment with atightly controlled oxygen environment. As with previous embodiments, inorder to form a densely packed solid, particles are accelerated to asufficient speed prior to hitting the surface. During the depositionprocess 20, particle temperature is raised to a sufficiently hightemperature to soften the particles and to enable deformation of theparticles to form a densely packed structure. As with previousembodiments, silicon may also be added as an alloying element to improvemagnetic properties while avoiding or minimizing the formation ofalumina.

The electromagnetic properties of the resulting soft magnetic material10 formed from any of the foregoing described morphologies of theparticle 22 include, but are not limited to, saturation flux density,permeability, energy loss due to hysteresis, and energy loss due to eddycurrents. A microstructure comprising densely packed micro-domains withsuitable magnetic properties, each surrounded by thin insulatingboundaries, provides such desired electro-magnetic properties. Themagnetic properties of the micro-domains and the insulating propertiesof the boundaries are in turn functions of one or more physical andchemical properties such as alloy composition, lattice structure,oxidation thermodynamics, and kinetics.

With regard to lattice structure, an alloy comprising 89% Fe-10% Al hasthe same body-centered cubic (BCC) structure as iron. This latticestructure is associated with a high magnetic permeability and suitablemagnetic properties. Furthermore, in the presence of 0.25% carbon, thealloy maintains its BCC structure up to a temperature of 1000 degrees C.The heat treatment enables the conversion of any face-centered cubicstructure and martensitic structures present in the solid into BCCstructure. The atomic fraction of aluminum in the alloy is about 20%and, therefore, the alloy has a saturation flux density that is about20% lower than that of pure iron. In addition, the alloy is known tohave an electrical resistivity greater than that of pure iron, resultingin lower eddy current losses.

Carbon in the range of about 0.25% may facilitate the gas atomizationprocess during powder production. Below about 1000 degrees C., carbon ispresent as carbide precipitates that may affect magnetic properties by,for example, lowering initial permeability and increasing hysteresisloss.

A suitable stable oxide that forms when the alloy particle is in anoxidizing environment at the temperature range of about 1000 degrees C.to about 1500 degrees C. is alumina. The rate of formation and expectedthickness of this oxide layer are determined by the oxidation kineticsof the alloy particles in the deposition environment. Elemental aluminumforms a 1-2 nanometer (nm) thick oxide layer, effectively blockingfurther oxidation. In addition, through oxidation kinetics simulationsusing software simulation packages, it was determined that pure ironparticles, sized at 25-40 microns and at a temperature of about 1500degrees C. develop a 500 nm thick oxide layer over the duration of theirflight (which is estimated to be about 0.001 seconds using thedeposition process 20 of any of the HVAF, HVOF, or plasma spray systemsdescribed herein). Therefore, the expected oxide layer around eachparticle is at least about 1 nm and up to about 500 nm in thickness.

Referring now to FIGS. 6A through 6D, in any embodiment, it is desiredto have isotropy in the magnetic properties of the sprayed samples. Theisotropy allows for the use of the material in motors with 3-dimensionalflow of magnetic flux. The magnetic properties measurable in thedisclosed embodiments are measureable along the circumferentialdirection of a ring-shaped sample (as shown in FIG. 6A) per the ASTMA773 standard. Even though measurements along the other two orthogonaldirections (axial and radial) may not be possible, the microstructure ofthe sample cross-section on the three orthogonal planes, shown in FIGS.6B, 6C, and 6D and corresponding to views along the XZ plane, YZ plane,and XY plane, respectively, shows the degree of isotropy in thematerial. Even though the micro-domains are, to some extent, stretchedalong the circumferential direction as this is the direction normal tothe direction of spray, they nevertheless exhibit a high degree ofisotropy in their shape.

Referring to FIGS. 7 through 40 and 46, various exemplary embodiments ofmotors in which the soft magnetic material 10 may be incorporated areshown. The motors described are intended to be driven as three-phasebrushless motors with sinusoidal commutation using position feedbackfrom high resolution rotary encoders.

Referring specifically to FIG. 7, a permanent magnet motor where a fluxflow is along a plane normal to an axis of rotation of the motor isshown generally at 100. The motor 100 has a rotor 102 of magnetic steel(or other suitable magnetic material) rotatably mounted in a stator 106.Magnets 104 are located on an outer radial surface of the rotor 102. Thestator 106 has a laminated steel core with stator poles 108 definedalong an inner edge of the stator 106 and windings or coils 110 locatedat each stator pole 108. The motor 100 may incorporate the soft magneticmaterial 10.

Referring to FIG. 8, the soft magnetic material 10 as described hereinmay be incorporated into an electric motor (e.g., as the stator or atleast a portion of the stator). One exemplary embodiment of a flux motorincorporating the soft magnetic material 10 is designated generally bythe reference number 200 and is hereinafter referred to as “motor 200.”Motor 200 is a three-dimensional flux motor having a rotor 202 rotatablymounted in a stator 206. The rotor 202 may be configured as a shaft. Aradially outer cylindrical surface of the rotor 202 defines a rotor pole212, and an inner edge of the stator 206 defines a stator pole 208. Thestator 206, along the stator pole 208, includes a plurality of slotswhich define cores around which coils 210 are disposed as individualwindings. In alternate configurations, however, coils formed asdistributed windings may be provided at the stator pole 208.

In the motor 200, magnets 204 are located at the rotor pole 212. Therotor pole 212 and the stator pole 208 in conjunction with the shapes ofthe magnets 204 direct magnetic flux between the rotor and the stator indirections that are outside of a single plane in three dimensions. Themagnets 204 may have a radially outer cylindrical surface that abuts twoconical surfaces and terminates with two smaller diameter cylindricalsurfaces. The magnets 204 are shown as being unitary in shape. However,in alternate embodiments the magnets may comprise individual segments toform the shape. Similarly, the stator pole 208 is configured toapproximate a Y-shaped cross-section that defines surfaces correspondingto the opposing surfaces on the magnets 204. The Y-shaped cross-sectionfurther allows flux flow along one or more of the radial, axial, and/orcircumferential directions of the motor within the stator.

A conical air gap 214 between the magnets 204 and the stator pole 208allows flux flow along the radial, axial, and circumferential directionsof the motor 200. Because the rotor pole 212 is extended in thedirection of the stator pole 208 and because the stator pole 208 is alsoextended in the direction of the rotor pole 212, a conicaltorque-producing area is defined in the conical air gap 214 between therotor pole 212 and the stator pole 208, which results in a higher torquecapacity when compared to the permanent magnet motor 100 as shown inFIG. 7. The larger conical torque-producing area defined by the conicalair gap 214 more than offsets the marginally lower torque producingradius and a marginally lower coil space.

The rotor 202 and/or the stator 206 (or at least the core of the stator206) may be made from the soft magnetic material 10 having a highsaturation flux density, permeability, and low energy loss due tohysteresis and energy loss due to eddy currents. A microstructurecomprising densely packed micro-domains with suitable magneticproperties, each surrounded by thin insulating boundaries may yield thedesired electro-magnetic properties facilitating the use of a magneticflux path in three dimensions as opposed to conventional motors thatutilize a magnetic flux path that is one-dimensional, for example, apath in a plane. Similarly, the further disclosed embodiments mayutilize such a material.

Referring now to FIG. 9, a variation of the three-dimensional flux motorwith a cylindrical air gap is shown generally at 300. In motor 300, arotor 312 is rotatably mounted in a stator 306 such that a rotor pole312 faces a stator pole 308. The stator 306 (or at least the corethereof) may comprise the soft magnetic material 10. Magnets 304 arelocated on the rotor pole 312. A torque-producing area defined by aconical air gap 314 between the magnets 304 on the rotor pole 312 andthe stator pole 308 is cylindrical and extended only along the axialdirection. In addition, an outer wall 307 of the stator 306 is extendedin the axial direction as well. This extension of the outer wall 307allows for the use of a thinner stator wall without compromising thestator wall cross-sectional area available for flux flow. The extensionof the outer wall 307 also provides for additional space for coils 310.Although the conical air gap 314 is cylindrical, due to the extendednature of the magnets 304 located on the rotor pole 312 and adjacent thestator pole 308, flux is directed in more than one plane, therebyresulting in a three-dimensional flux pattern.

Referring now to FIGS. 10A and 10B, another exemplary embodiment of aflux motor is shown generally at 400. As with previously disclosedembodiments, motor 400 comprises a rotor 402 rotatably located in astator 406. The stator 406 includes a stator pole 408 and coils 410, thecross-sectional areas of each coil 410 being maximized by thecross-sectional areas of the stator pole 408 by both the coils 410 andthe stator pole 408 being tapered along the radial direction. Morespecifically, the circumferential dimension of each of coil 410 istapered along an interface 416 such that the circumferential dimensionof each of coil 410 increases with radius, while the axial dimension ofthe stator pole 408 is tapered along the interface 416 such that theaxial dimension of the stator pole 408 decreases with radius. Eventhough the examples disclosed herein depict permanent magnet motors, inalternate aspects any of the disclosed embodiments are applicable tovariable reluctance motors (e.g., non-permanent magnetic poles) or anyother suitable motor. The tapered stator pole 408 in combination withthe extended stator pole faces facilitate magnetic flux between thestator 406 and rotor 402 in more than one plane.

Referring to FIG. 10B, one exemplary embodiment of the stator pole 408illustrating a two-dimensional taper is shown. As can be seen, axialdimensions of the stator pole 408 decrease from a height H₁ to a heightH₂ with increasing radius. In addition, a circumferential width of thestator pole 408 increases from a width W₁ to a width W₂ in the radialdirection to preserve a “tooth area” of the cross-section of the statorpole 408. In one exemplary aspect, the cross-sectional area of thetapered portion of the stator pole 408 may be maintained constant suchthat the flux density within the stator pole 408 may be maintainedacross the section.

Referring now to FIG. 11, another exemplary variation of a motor isshown generally at 500. Motor 500 allows axial assembly of a rotor 502and a stator 506. The embodiment is similar to that of FIG. 10A and FIG.10B except that only one end is of the rotor 502 and the stator 506 isangled (along surface 520) while the other end is straight orcylindrical (along surface 522). The embodiment shown in FIG. 11 allowsthe rotor 502 to be axially assembled to the stator 506. In alternateembodiments, aspects of any of the disclosed embodiments may be combinedin any suitable combination.

Referring now to FIG. 12, a motor 600 has a rotor 602 and a split stator606 to facilitate assembly of the stator 606 about the rotor 602 priorto or after winding. As shown, motor 600 may have features similar tothose illustrated above. However, the split stator 606 allows for therotor 602 to be of a single unitary construction where a first statorportion 607 and a second stator portion 609 may be assembledcircumferentially about the rotor 602, each of the two portions 607, 609being joined at a separation line 611 that lies in a plane where theflux would be directed in a planar direction. Portions of the splitstator 606 on opposing sides of the separation line 611 direct the fluxbetween the rotor 602 and the split stator 606 in directions thatinclude more than one plane resulting in a three-dimensional fluxpattern.

Referring now to FIG. 13, another exemplary embodiment of a motor 700comprises a rotor 702 and a split stator 706 in which the split stator706 is divided into three layers (an inner portion 707, a middle portion709, and an outer portion 713) around which a coil 710 is wound. Themiddle portion 709 may be fabricated of a material (e.g., laminatedsteel or the like) that is different from the inner portion 707 and theouter portion 713. In the middle portion 709, the flux flow may besubstantially planar substantially. The inner portion 707 and the outerportion 713 may be fabricated of materials that facilitate athree-dimensional flux flow.

As shown in FIGS. 14A and 14B, another exemplary embodiment of a motor800 comprises a split concave rotor 802 having first and second rotorportions 803, 805 each with respective magnets 807, 809, each of thefirst and second rotor portions 803, 805 being axially assembled into astator 806. The split configuration of the rotor 802 allows for thestator 806 to be of a single unitary construction such that the firstand second rotor portions 803, 805 of the rotor 802 may be assembledabout the stator 806, for example, after winding the coils 810. Aseparation line 817 lies in a plane where the flux would be directed ina planar direction. Portions of the rotor 802 on opposing sides of theseparation line 817 direct flux between the rotor 802 and the stator 806in directions that include more than one plane, thereby resulting in athree-dimensional flux pattern. In alternate aspects, the stator 806could also be split into two or more layers. For example, in a stator806 split into three portions, a middle portion may be made of laminatedsteel, for example, as previously disclosed. Motor 800 allows flux flowalong the radial, axial, and circumferential directions. Because themotor 800 has stator poles 808 and rotor poles 812 that extend in radialdirections, there is an additional conical torque producing air gap areathat results in a higher torque capacity, when compared with aconventional motor. Here, the larger torque producing area more thanoffsets the marginally lower torque producing radius and a marginallylower coil space. As in each of the previously-disclosed embodiments,the rotor 802 and/or stator 806 may be made from the soft magneticmaterial 10 having a high saturation flux density, permeability, and lowenergy loss due to hysteresis and energy loss due to eddy currents. Amicrostructure of the soft magnetic material 10 comprising the denselypacked micro-domains with suitable magnetic properties, each surroundedby thin insulating boundaries may yield desired electro-magneticproperties facilitating the use of a magnetic flux path in threedimensions as opposed to conventional motors that utilize a magneticflux path that is one-dimensional, for example, a path in a plane.Similarly, the further disclosed embodiments may utilize such amaterial. In alternate embodiments, aspects of any of the disclosedembodiments may be combined in any suitable combination.

Still referring to FIGS. 14A and 14B, the magnets 807, 809 are shown atthe rotor poles 812 having two radially outer cylindrical surfaces thatabut two conical surfaces of each respective rotor portion 803, 805 andterminate with two smaller diameter cylindrical surfaces. The magnets807, 809 are shown as being unitary in this shape but alternately may bemade of segments to form the shape. The stator pole 808 has similarlyshaped surfaces corresponding to the opposing surfaces on the magnets803, 805. The pole shapes in combination with the magnet shapes directmagnetic flux between the rotor 802 and the stator 806 in directionsthat are outside of a single plane in three dimensions. The coils 810shown are shown as individual windings wrapped about individual statorpoles 808. In alternate aspects, the coils 810 may comprise distributedwindings.

Referring now to FIGS. 15A and 15B, a motor 900 is shown as having asplit concave rotor 902 and a split stator 906. The split concave rotor902 has a first rotor portion 903 and a second rotor portion 905, andthe split stator 906 has a first stator portion 907 and a second statorportion 909. In contrast to the split stator 706 shown in FIG. 13, eachof the first stator portion 907 and the second stator portion 909 hasits own coils 910, 911 such that each of the first stator portion 907and the second stator portion 909 can be wound prior to assembly of thestator 906 with the rotor 902. Here, the split concave rotor 902 allowsfor the split stator 906 to be preassembled and wound where the firstrotor portion 903 and the second rotor portion 905 may be assembledabout the stator 906, for example, after winding. The stator 906 issplit such that the motor 900 allows flux flow along the radial, axial,and circumferential directions. Because the motor 900 has extended rotorpoles 912 and stator poles 908, there is an additional conical torqueproducing air gap area that results in a higher torques capacity ascompared to a conventional motor. The larger torque producing area morethan offsets the marginally lower torque producing radius and amarginally lower coil space. As in each of the disclosed embodiments,the rotor 902 and/or the stator 906 may be made from the soft magneticmaterial 10 with a high saturation flux density, permeability, and lowenergy loss due to hysteresis and energy loss due to eddy currents. Amicrostructure of the soft magnetic material 10 comprising the denselypacked micro-domains with suitable magnetic properties, each surroundedby thin insulating boundaries may yield desired electro-magneticproperties facilitating the use of a magnetic flux path in threedimensions as opposed to conventional motors that utilize a magneticflux path that is one-dimensional, for example, a path in a plane.Similarly, the further disclosed embodiments may utilize such amaterial. In alternate embodiments, aspects of any of the disclosedembodiments may be combined in any suitable combination.

Also as shown in FIGS. 15A and 15B, the magnets 930, 932 are shown atthe rotor poles 912 having two radially outer cylindrical surfaces thatabut two conical surfaces of each respective rotor portion 903, 905 andterminate with two smaller diameter cylindrical surfaces. The magnets930, 932 are shown as being unitary in this shape but alternately may bemade of segments to form the shape. The stator poles 908 similarly areshaped poles that have surfaces corresponding to the opposing surfaceson the magnets 930, 932. The pole shapes in combination with the magnetshapes direct magnetic flux between the rotor 902 and the stator 906 indirections that are outside of a single plane in three dimensions. Thecoils 910 shown are shown as individual windings wrapped aboutindividual stator poles 908. In alternate aspects, the coils 910 maycomprise distributed windings.

Referring now to FIGS. 16A and 16B, a motor 1000 is shown as having asplit convex rotor 1002 axially assembled with a split stator 1006. Thesplit convex rotor 1002 comprises a first rotor portion 1003 and asecond rotor portion 1005. In alternate aspects, the rotor 1002 may notbe split but may instead comprise a unitary piece. The split stator 1006comprises a first stator portion 1007 and a second stator portion 1009,each portion of the stator having its own set of coils 1010, 1011. Eachstator portion 1007, 1009 can be wound prior to assembly. The stator1006 is split such that the motor 1000 allows flux flow along theradial, axial, and circumferential directions. Because the motor 1000has extended rotor poles 1012 and stator poles 1008, there is anadditional conical torque producing air gap area that results in ahigher torques capacity as compared to a conventional motor. The largertorque producing area more than offsets the marginally lower torqueproducing radius and a marginally lower coil space. As in each of thedisclosed embodiments, the rotor 1002 and/or the stator 1006 may be madefrom the soft magnetic material 10 with a high saturation flux density,permeability, and low energy loss due to hysteresis and energy loss dueto eddy currents. A microstructure of the soft magnetic material 10comprising the densely packed micro-domains with suitable magneticproperties, each surrounded by thin insulating boundaries may yielddesired electro-magnetic properties facilitating the use of a magneticflux path in three dimensions as opposed to conventional motors (thatutilize a magnetic flux path that is one-dimensional, for example, apath in a plane. Similarly, the further disclosed embodiments mayutilize such a material. In alternate embodiments, aspects of any of thedisclosed embodiments may be combined in any suitable combination.

Still referring to FIGS. 16A and 16B, the magnets 1030, 1032 are shownat the rotor poles 1012 having two radially outer cylindrical surfacesthat abut two conical surfaces of each respective rotor portion 1003,1005 and terminate with two smaller diameter cylindrical surfaces. Themagnets 1030, 1032 are shown as being unitary in this shape butalternately may be made of segments to form the shape. The stator poles1008 similarly are shaped poles that have surfaces corresponding to theopposing surfaces on the magnets 1030, 1032. The pole shapes incombination with the magnet shapes direct magnetic flux between therotor 1002 and the stator 1006 in directions that are outside of asingle plane in three dimensions. The coils 1010, 1011 shown are shownas individual windings wrapped about individual stator poles 1008. Inalternate aspects, the coils 1010, 1011 may comprise distributedwindings.

Referring now to FIGS. 17A through 17C, schematic views of stator crosssections are shown. FIG. 17A shows the motor coil 110, stator pole 108,and stator wall 140 in a cross-section. The stator cross section area isdenoted by height 142 and width 144 where the coil 110 may have a width150 and a pole axial height 152. The stator pole 108 may be made oflaminated steel suitable for motor stators. As will be described for agiven area defined by the height 142 by the width 144, with the use ofthe soft magnetic material (for example, in FIGS. 17B and 17C) hereindescribed allowing three-dimensional flux flow within the stator, thecross section may be more efficiently utilized. For example, in FIG.17B, a coil 1110, a stator pole 1108, and a stator wall 1140 are shownwhere a decreased width 1176 and where the stator wall 1140 is axiallylonger by a length 1178 may be provided to increase the cross-sectionalarea of the coil 1108 and a length 1180. A pole axial height 1190 isalso shown. By way of further example, in FIG. 17C, a coil 1210, statorpole 1208, and a stator wall 1240 are shown where, as in FIG. 17B, athinner and axially longer stator wall 1240 may be provided to increasestator pole cross-section area but also where the coil 1210 is wider butthinner to maintain same area as the coil in FIG. 17A. Here, the poleaxial height 1290 may be larger than the pole axial height 1190 FIG.17B.

Referring now to 18A through 18C, a section of another exemplaryembodiment of a motor 1300 has a convex rotor 1302 and a split stator1306. Each half of the stator 1306 has its own set of windings. Althougha single rotor 1302 and stator 1306 are shown, in alternate aspectsmultiple rotors and/or stators may be stacked. The embodiment shownincludes a triangular cross section and may be configured with a singletriangular cross section or multiple cross sections, for example,concave or convex cross sections. Further, in alternate aspects, themotor 1300 may be provided with a concave rotor or any suitable shape.Each portion of the stator 1307, 1309 can be wound prior to assembly.Stator portions 1307, 1309 have angled windings 1310 wound about taperedpoles 1308. Flux is directed from pole to pole by a stator wall 1340where the stator wall 1340 has a triangular shape section in the upperand lower corners of the stator 1306. The side section of FIG. 18A showsa stator pole 1308 tapered with the cross section increasing axiallytoward the rotor 1302. The top section of FIG. 18B shows the stator pole1306 tapered with the cross section decreasing axially toward the rotor.Here, with the combination of tapers, the cross sectional area of thestator pole 1306 may be maintained. The split configuration of thestator 1306 allows for the stator 1306 to be preassembled and woundwhere the two stator portions 1307, 1309 may be assembled about therotor 1302, for example, after winding. The stator 1306 is shown splitwhere the motor 1300 allows flux flow along the radial, axial, andcircumferential directions. Because the motor 1300 has extended rotorpoles and stator poles, as previously described in other exampleembodiments, there is an additional conical torque producing air gaparea that results in a higher torque capacity, when compared with aconventional motor. The larger torque producing area more than offsetsthe marginally lower torque producing radius and a marginally lower coilspace. As in each of the disclosed embodiments, the rotor 1302 and/orthe stator 1306 may be made from the soft magnetic material 10 with ahigh saturation flux density, permeability, and low energy loss due tohysteresis and energy loss due to eddy currents. A microstructure of thesoft magnetic material 10 comprising the densely packed micro-domainswith suitable magnetic properties, each surrounded by thin insulatingboundaries may yield desired electro-magnetic properties facilitatingthe use of a magnetic flux path in three dimensions as opposed toconventional motors that utilize a magnetic flux path that isone-dimensional, for example, a path in a plane. Similarly, the furtherdisclosed embodiments may utilize such a material. In alternateembodiments, aspects of any of the disclosed embodiments may be combinedin any suitable combination.

Referring now to FIGS. 18A and 18C, the magnets 1340, 1342 are shown atthe rotor poles 1312 having two radially outer cylindrical surfaces thatabut two conical surfaces of each respective rotor portion 1307, 1309and terminate with two smaller diameter cylindrical surfaces. Themagnets 1340, 1342 are shown as being unitary in this shape butalternately may be made of segments to form the shape. The stator poles1308 similarly are shaped poles that have surfaces corresponding to theopposing surfaces on the magnets 1340, 1342. The pole shapes incombination with the magnet shapes direct magnetic flux between therotor 1302 and the stator 1306 in directions that are outside of asingle plane in three dimensions. The coils 1310 shown are shown asindividual windings wrapped about individual stator poles 1308. Inalternate aspects, the coils 1310 may comprise distributed windings.

Referring now to FIG. 19, a section of a motor 1400 having a convexrotor 1402 and a stator 1406 is shown. Although a single rotor 1402 anda single stator 1406 are shown, in alternate aspects, multiple rotorsand/or stators may be stacked. Stator 1406 has angled windings 1410wound about tapered poles 1408. Flux is directed from pole to pole by astator wall 1440 where the stator wall 1440 has a triangle-shapedsection in the upper corner of the stator 1406. In the embodiment shown,the triangle-shaped section has a width at the termination of the pole1408 that is wider allowing for additional winding area for the winding1410. Similarly, the pole 1408 faces opposing the magnets of rotor 1402may be extended as shown or otherwise to increase additional windingarea for the winding 1410. In alternate embodiments, aspects of any ofthe disclosed embodiments may be combined in any suitable combination.

Referring now to FIGS. 20 and 21, there are shown isometric sectionviews of a stator 1506 and a rotor 1502, respectively. In the exemplaryembodiments shown, inwardly angled stator teeth 1550 are located at anangle to be normal with the orientation of the outwardly angled magnets1540. Such an arrangement makes use of available space and increases thecross-sectional area for flux flow. The teeth 1550 have upper 1552 andlower 1554 portions that overlap coils 1510 such that flux flows acrossthe entire cross section of each of the stator teeth 1550. Similarly,portions overlap coils 1510 of a stator ring 1556 such that flux flowsacross the entire cross section of the stator ring 1556 from tooth totooth of the stator 1506. Although individual windings are shown foreach pole, distributed windings may alternately be provided.

Referring now to FIGS. 22 and 23, there is shown arrangements of anassembled rotor 1602 and stator 1606. In one exemplary aspect, a singlestator 1606 and rotor 1602 may be provided. As seen in FIG. 22, thestator 1606 may comprise a first stator portion 1607 and a second statorportion 1609, and the rotor 1602 may comprise a first rotor portion 1603and a second rotor portion 1605. The stator 1606 and rotor 1602 may beassembled such that the first and second stator portions form twotriangular cross sections mating radially at the narrow portion of thetriangular cross section. As seen in FIG. 23, the first stator portion1607 and the second stator portion 1609 along with the first rotorportion 1603 and the second rotor portion 1605 may alternately beassembled such that the stator portions form two triangular crosssections mating radially at the wide portion of the triangular crosssections. In alternate aspects, any suitable combination may beprovided. The stator teeth are convex and the rotor teeth are concave.

The exemplary embodiments of FIGS. 20 through 23 may not allow forindependent sizing of tooth cross-sectional area and coilcross-sectional area. As a result, larger tooth cross-section comes atthe expense of smaller coil cross-section and vice versa. Theembodiments of FIGS. 24-29, as described below, provide options to alterthe tooth cross sections independently in order to achieve an optimaldesign. However, this flexibility comes at the expense of a smallermagnet area. The embodiment as shown in FIG. 20, however, is a specialcase of the embodiment as shown in FIG. 27, for example, when a=0 inFIG. 27. For example, setting a=0 and yields the embodiment of FIGS.20-23.

Referring now to FIGS. 24 and 25, there are shown isometric sectionviews of a rotor 1702 and a stator 1706, respectively. Referring also toFIG. 26, the rotor 1702 and the stator 1706 are shown assembled. Asshown in FIG. 26, a single stator 1706 and a single rotor 1702 may beprovided. As shown in FIG. 28, the stator 1706 may comprise a firststator portion 1707 and a second stator portion 1709, both of which maybe assembled with the rotor 1702 comprising a first rotor portion 1703and a second rotor portion 1705 to form two cross sections matingradially at the wide portion of the cross sections.

As shown in FIG. 29, a stator 1806 may comprise a first stator portion1807 and a second stator portion 1809, both of which may be assembledwith a rotor 1802 comprising a first rotor portion 1803 and a secondrotor portion 1805 to form two cross sections mating radially at thewide portion of the cross sections.

Referring back to FIG. 27, there is shown a stator pole cross-sectionshowing variable parameters. In the embodiment shown, the stator teeth1550 have faces 1562, 1564, and 1566 located at various angles to benormal with the orientation of the magnets. Such an arrangement makesuse of available space, and increases the cross-sectional area for fluxflow. The teeth 1550 have upper 1552 and lower 1554 portions thatoverlap the coils 1510 such that flux flows across the entire crosssection of the stator tooth 1550. Although individual windings are shownfor each pole, distributed windings may alternately be provided. Thestator tooth 1550 has a section 1570 with a varying cross section suchthat the coil 1510 denoted by measurement parameters a, b, c, and d maybe optimized. In alternate aspects, any suitable combination may beprovided.

Referring now to FIGS. 30 and 31, isometric section views of a stator1906 and a rotor 1902 are respectively shown. The exemplary embodimentillustrated includes a slotless stator design in which the stator 1906has a soft magnetic core 1912 and a potted winding 1914. The softmagnetic core 1912 is defined directly on a surface of the stator 1906(thus avoiding the use of slots) and may comprise the soft magneticmaterial 10, as described above. As shown, the rotor 1902 may be atwo-piece rotor as illustrated in FIGS. 31 and 32 (comprising a firstrotor portion 1903 and a second rotor portion 1905). Alternately, amotor may be made with just one half of the rotor 1902 and the stator1906.

Referring now to FIG. 33, another exemplary embodiment of a slotlessmotor is shown generally at 2000. Slotless motor 2000 comprises a rotor2002 rotatably mounted to a slotless stator 2006. The rotor 2002comprises a first rotor portion 2003 and a second rotor portion 2005,both portions being symmetrical. The slotless stator 2006 comprises awall 2007 and a backing portion 2009 that form a continuous portionhaving a constant cross section. Magnets 2014 are mounted between therotor 2002 and the slotless stator 2006. Windings in the form of coils2010 are self-supported and evenly distributed on an inner-facingsurface around the slotless stator 2006 and have a horizontal V-shapedcross section. Motor 2000 is further described with regard to Example 3below.

Referring now to FIGS. 34 through 40, a slotless brushless permanentmagnet motor into which the soft magnetic material as described hereinmay be incorporated is shown generally at 2100. Motor 2100 is a hybridmotor. As can be seen in FIGS. 34 and 37, an air gap cross section 2110is V-shaped and may include a spacer 2112.

As shown in FIGS. 35A through 35E, a stator assembly of the motor 2100is shown generally at 2120. As can be seen in FIG. 35C, the statorassembly 2120 has a cutout 2130 at a back wall 2135 thereof (the backwall 2135 follows the profile of the coils) to allow for cooling linesor the like. The cutout 2130 may have any suitable shape and may beprovided to reduce material consumption. The cutout 2130 may also beshaped for uniform flux distribution in one or more portions of thestator, for example, between the windings or poles or the like. As shownin FIG. 35E, a core 2140 of the stator assembly 2120 is made of amaterial with isotropic magnetic properties. FIGS. 35A, 35B, and 35Cshow the stator cross-section with winding coils 2150 overlaid on thestator core 2140. As shown in FIG. 40, the winding coils 2150 may becoupled to the core 2140 using a potting material 2165. An outer surface2166 of the potting material 2165 may provide for winding leads andthermocouple leads. Overall, the motor 2100 has a diameter defined by adiameter of the stator D1 (diameter D2 to the outer surface 2166) and aheight H.

FIG. 35D shows an individual winding coil 2150. Three winding coils, oneof each phase, may have thermocouples embedded in them. In one exemplaryembodiment, the stator assembly 2120 is Wye-wound with 4 flying leads (3line leads and 1 center tap). Since the stator assembly 2120 may beaxially clamped, the flying leads will exit the stator ring at the outerdiameter through the outer surface 2166. The stator core 2140 and thewinding coils 2150 may be potted using the potting material 2165 toprovide one integrated “stator ring.”

An individual winding coil 2150 is shown in FIG. 35D and FIG. 38. Thewinding coils 2150 each have a rectangular cross-section that variesalong the coil length. The coil cross-section width increases withradius and its thickness decreases so that the area of cross-sectionremains more or less constant along its length. FIG. 38 illustrates thisconcept. The wire may be 25 AWG, with insulation layer that is stable upto 120 degrees C. or class H. The coil is alpha-wound with start andfinish on the outside. In accordance with the varying cross-section ofthe coils, the wire grid changes from an 8×6 grid to a 10×5 grid alongthe length of the coil to make optimal use of space. The windingthickness decreases with increasing radius. The air gap clearance isthus reduced accordingly. Note that this is a suggested grid pattern.Alternate more efficient grid patterns that satisfy the spatialconstraints of the windings may be employed.

Referring now to FIGS. 34 and 36, a rotor assembly of the motor 2100 isshown generally at 2115. To facilitate assembly, the rotor assembly 2115is comprised of two substantially identical halves, one of which isshown in FIG. 36C, and each being magnetized in a different direction(or having a continuously varying magnetization direction in anindividual pole). The rotor assembly 2115 may also be made of a singlering in which case the magnetization will vary continuously in twoorthogonal directions (circumferentially and along the pole length). Therotor halves may be made of low-carbon steel such as 1018 steel. Toprevent corrosion, the rotor halves may be powder coated.

The rotor assembly 2115 has a plurality of rotor poles, each comprisingtwo magnet pieces 2160. FIG. 36E shows one of the rotor halves and oneof the magnets 2160 attached to it. There may be about 30 magnets 2160in each rotor half, each magnetized in the radial direction. Neighboringmagnets are magnetized in diametrically opposite directions. Rotormagnets 2160 may be made of Neodymium with a remanence flux density ofapproximately 1.3. A magnet with properties similar to N42UH or N42SH orequivalent may be used. The magnet shapes may be cut from apre-magnetized block and finished by grinding. FIGS. 36D and 39 show thetwo magnet pieces that comprise a pole in one rotor half. Each piece maybe magnetized as shown such that the magnetization is parallel, notradial. Upon grinding, the magnets 2160 may be coated to preventcorrosion.

As an alternative to the hybrid motor 2100, a radial flux motor may beemployed. Such a motor may utilize a 3-phase brushless DC motor withslotless windings. In such a motor, the stator may be made of laminatedsilicon steel.

In one embodiment, a soft magnetic material comprises a plurality ofiron-containing particles and an insulating layer on the iron-containingparticles. The insulating layer comprises an oxide. The soft magneticmaterial is an aggregate of permeable micro-domains separated byinsulation boundaries. The oxide of the insulating layer may comprisealumina. The iron-containing particles may have a body-centered cubicstructure. The iron-containing particles may include silicon. Theiron-containing particles may include at least one of aluminum, cobalt,nickel, and silicon.

In another embodiment, a soft magnetic material comprises a plurality ofiron-containing particles, each of the iron-containing particles havingan alumina layer disposed on the iron-containing particles. Anarrangement of the iron-containing particles with the alumina layersforms a body-centered cubic lattice micro-structure that defines anaggregate of micro-domains having high permeability and low coercivity,the micro-domains being separated by insulation boundaries. Theiron-containing particles may comprise about 89 wt. % iron, about 10 wt.% aluminum, and about 0.25 wt. % carbon. The iron-containing particlesmay include silicon. The iron-containing particles may include at leastone of aluminum, cobalt, nickel, and silicon. The iron-containingparticles may be defined by a core of a uniform composition ofiron-containing and the alumina layer may comprise substantially purealuminum oxide. The soft magnetic material may be defined by particleshaving a core of a uniform composition of iron-aluminum alloy, and thealumina layer may be defined by a concentration gradient consistingessentially of zero aluminum oxide at a surface of the core toessentially pure aluminum oxide at an outer surface of the aluminalayer. The body-centered cubic lattice micro-structure may besubstantially isotropic in an XZ, YZ, and XY plane.

In one embodiment of making the soft magnetic material, a methodcomprises providing an iron-aluminum alloy particle; heating theiron-aluminum alloy particle to a temperature that is below the meltingpoint of the iron-aluminum alloy particle but sufficiently high enoughto soften the iron-aluminum alloy particle; thermally spraying theiron-aluminum alloy particle; causing the iron-aluminum alloy particleto oxidize; depositing the iron-aluminum alloy particle onto asubstrate; subsequently building up a bulk quantity of the iron-aluminumalloy particle on the substrate and on successive layers of theiron-aluminum alloy particle deposited on the substrate; and heattreating the bulk quantity of the iron-aluminum alloy particles. Theiron-aluminum alloy particle may comprise an alloy having a compositionof about 89 wt. % iron, about 10 wt. % aluminum, and about 0.25 wt. %carbon. Heating the iron-aluminum alloy particle may comprise heating toless than about 1450 degrees C. Thermally spraying the iron-aluminumalloy particle may comprise gas-atomizing the iron-aluminum alloyparticle in a carrier gas. Thermally spraying the iron-aluminum alloyparticle may comprise using a high velocity air fuel system in which acarrier gas operates at about 900 degrees C. to about 1200 degrees C. togas-atomize the iron-aluminum alloy particle. Thermally spraying theiron-aluminum alloy particle may comprise using a high velocity oxy fuelsystem operating at about 1400 degrees C. to about 1600 degrees C. todeposit the iron-aluminum alloy particle as a thin coating. Thermallyspraying the iron-aluminum alloy particle may comprise using a lowenergy plasma spray. Causing the iron-aluminum alloy particle to oxidizemay comprise forming alumina on an outer surface of the iron-aluminumalloy particle.

In one embodiment, a motor comprises a stator comprising at least onecore; a coil wound on the at least one core of the stator; a rotorhaving a rotor pole and being rotatably mounted relative to the stator;and at least one magnet disposed between the rotor and the stator. Theat least one core comprises a composite material defined byiron-containing particles having an alumina layer disposed thereon. Therotor pole and the stator in conjunction with the at least one magnetmay direct magnetic flux between the rotor and the stator in directionsthat are outside of a single plane in three dimensions. The stator maybe configured to approximate a cross sectional shape that definessurfaces corresponding to a cross sectional shape of the at least onemagnet. A conical air gap may be located between the stator and the atleast one magnet, wherein the conical air gap allows flux flow alongradial, axial, and circumferential directions of the motor. The rotorpole may be extended in the direction of the stator to produce theconical air gap between the stator and the at least one magnet. The coilmay be tapered in the radial direction. The at least one core may beformed on a surface of the stator to form a slotless stator. The rotormay comprise a first rotor portion and a second rotor portion. Thestator may comprise at least a first stator portion and a second statorportion.

In another embodiment, a motor comprises a slotless stator comprising atleast one core formed of a soft magnetic composite material and coilsdisposed on the at least one core; a rotor rotatably mounted relative tothe slotless stator; and at least one magnet mounted on the rotorbetween the rotor and the slotless stator. The soft magnetic compositematerial may comprise particles containing at least iron and havinginsulating outer surfaces comprising alumina. The particles containingat least iron may comprise an iron-aluminum alloy. The motor may includean air gap between the slotless stator and the at least one magnet, theair gap being conical in cross sectional shape. The slotless stator maycomprise a wall that forms a continuous surface on which the at leastone core is formed. The soft magnetic material may comprise about 89 wt.% iron, about 10 wt. % aluminum, and about 0.25 wt. % carbon. The softmagnetic material may further comprise silicon.

In another embodiment, a slotless flux motor comprises a stator definedby a continuous surface at which at least one core is disposed and awinding disposed on the at least one core; a rotor having a rotor poleand being rotatably mounted in the stator; and at least one magnetmounted between the stator and the rotor pole. A conical air gap isdefined between the stator and the at least one magnet, wherein theconical air gap allows flux flow along radial, axial, andcircumferential directions of the motor. The at least one core comprisesa soft magnetic composite material defined by iron-containing particlesencapsulated in alumina. The iron-containing particles may comprise aniron-aluminum alloy that may comprise about 89 wt. % iron, about 10 wt.% aluminum, and about 0.25 wt. % carbon. The iron-containing particlesmay further comprise silicon. The iron-containing particles of the softmagnetic composite material may include one or more of iron-cobaltalloy, iron-nickel alloy, and iron-silicon alloy. The at least one coremay be self-supported on an inner-facing surface of the stator and havea horizontal V-shaped cross section.

One embodiment of a composition comprises a plurality of iron-containingparticles and an insulating layer on the iron-containing particles. Theiron-containing particles define an aggregate of permeable micro-domainsseparated by insulation boundaries. The insulating layer may comprise anoxide. The oxide may be aluminum oxide. The iron-containing particlesmay have a body-centered cubic structure. The body-centered cubicstructure may be substantially isotropic in three dimensions. Theiron-containing particles may include at least one of aluminum, cobalt,nickel, and silicon. The aggregate of permeable micro-domains may have ahigh permeability and a low coercivity. The iron-containing particlesmay comprise about 89 wt. % iron, about 10 wt. % aluminum, and about0.25 wt. % carbon. The insulating layer may be defined by an oxide layerhaving a concentration gradient. The iron-containing particles and theinsulating layer may define a soft magnetic material.

One embodiment of a method comprises heating an iron-aluminum alloyparticle; thermally spraying the iron-aluminum particle; causing theiron-aluminum particle to oxidize; and depositing the oxidizediron-aluminum particle on a substrate. The iron-aluminum alloy particlemay comprise about 89 wt. % iron, about 10 wt. % aluminum, and about0.25 wt. % carbon. Heating the iron-aluminum alloy particle may compriseheating to less than about 1450 degrees C. Thermally spraying theiron-aluminum alloy particle may comprise spraying using a high velocityair fuel system, a high velocity oxy fuel system, or a low energy plasmaspray. Causing the iron-aluminum particle to oxidize may compriseforming alumina on an outer surface of the iron-aluminum alloy particle.Depositing the oxidized iron-aluminum particle on a substrate maycomprise forming a soft magnetic material.

One embodiment of an apparatus comprises a stator having at least onecore; a coil on the at least one core; a rotor rotatably mounted in thestator; and at least one magnet mounted between the stator and therotor. The at least one core comprises a composition defined byiron-containing particles having an oxide layer disposed thereon. Thestator may be slotless. The magnetic flux may be directed between therotor and the stator in three dimensions. The apparatus may furthercomprise a rotor pole defined by an outer-facing surface of the rotorand a stator pole defined by an inner-facing surface of the stator,wherein the at least one magnet is mounted on the outer-facing surfaceof the rotor. A cross sectional shape of the at least one magnet maydefine surfaces that correspond to a cross sectional shape of theinner-facing surface of the stator. The at least one magnet and theinner-facing surface of the rotor may define a conical air gap betweenthe rotor and the stator. The conical air gap may allow flux flow alongradial, axial, and circumferential directions of the apparatus. Thecomposition defined by iron-containing particles may have an oxide layercomprises a soft magnetic material. The iron-containing particles maycomprise an alloy having about 89 wt. % iron, about 10 wt. % aluminum,and about 0.25 wt. % carbon. The oxide layer may be aluminum oxide. Thecomposition may further comprise silicon. The composition may comprise aconcentration gradient in the oxide layer.

Referring to FIGS. 41 through 45, various exemplary aspects of themanufacture of the soft magnetic material 10 are described in thefollowing Examples.

Example 1

In the deposition processes 20 described herein, due to its higherdeposition efficiency, the HVAF system was selected to produce materialsamples for characterization of the insulation boundaries andelectromagnetic properties. Two different HVAF settings were selectedfor assessing the material properties. The first setting corresponded toa fuel-air mixture at the stoichiometric ratio. The second settingcorresponded to a leaner mixture resulting in a lower carrier gastemperature. The second setting produced a microstructure with a lowerpercentage of fully molten particles. A subset of the samples producedby both settings was also subjected to a heat treatment process in whichthe samples were heated to and held at a temperature of 1050 degrees C.(50 C degrees above the eutectic temperature) for 4 hours in a reducingenvironment, and then slowly cooled to room temperature to producesamples 1A and 2A, respectively, as shown in Table 1 (below). Thesamples were produced in the form of thin rectangular specimens as wellas rings of about 2 inches in diameter and about 0.25 inches thickness.The thin rectangles were used to study the microstructure under anelectron microscope as well as in an X-ray diffraction system. The ringswere used to characterize the magnetic properties per the ASTM A773standard.

The cross-sections of the thin rectangular samples were polished,etched, and observed under the electron microscope as well as an EnergyDispersive Spectroscopy (EDS) system to produce an elemental map acrossthe cross-section. FIG. 41 shows a cross-section of the sample 2A(Electron Image 1) as well as elemental maps corresponding to theelements iron, aluminum, and oxygen. Oxygen atoms are primarilyconcentrated at the particle boundaries, and iron atoms are absent atthe particle boundaries. There is a larger concentration of aluminumatoms at the boundaries than in the particle interior, indicating thatthe particle boundaries are composed of alumina, which is an excellentelectrical insulator, and the particle interior is composed of Fe—Alalloy, which is a desirable soft-magnetic material. In support of theabove finding, FIG. 42 shows an X-ray diffraction spectrum of thematerial, confirming the presence of alumina along with the Fe—Al alloy.

Thus, an insulation layer composed of alumina may be stable at hightemperatures (unlike an insulation layer made of iron-oxide). From theelectron microscope images, the thickness of the insulation boundarieswas estimated to be in the range of 100 nm to about 500 nm.

Measurements of magnetic properties were also performed per the ASTMA773 standard on ring-shaped samples shown in FIG. 41. The followingproperties were measured on samples 1, 1A, 2 and 2A: magnetizationcurves (B—H curves) up to a magnetizing field of 40 kA/m, flux densityat 40 kA/m, B_(sat@40 kA/m), coercivity, H_(c), magnetizing field at aflux density of 1 T, H_(1T), relative permeability at zero flux density,m_(r), DC energy loss (due to hysteresis), and AC power loss at 60 Hzand 400 Hz oscillations of the magnetic flux density. Table 1 shows theresults for the samples.

TABLE 1 Measured magnetic properties of ring samples 1, 2, 1A, and 2A,compared against a phase-1 sample (shown as P1) DC energy AC powerB_(sat@40 kA/m) H_(c) H_(req.1T) loss per cycle loss (W/kg) Sample (T)(A/m) (A/m) μ_(r) (J/kg) 60 Hz 400 Hz P1 0.9 700 41000 459 2237 39 685 11.31 3650 15400 230 9500 105.6 835 2 1.28 3500 17700 207 9725 93.5 7661A 1.42 420 2700 2500 1600 26.5 657 2A 1.35 615 8800 830 2100 24.8 306

For use of soft magnetic materials as disclosed herein in an electricmotor, the saturation magnetic flux density and relative permeabilityshould be maximized, and the required magnetizing field, coercivity, DCenergy loss, and AC power loss should be minimized. The results in Table1 show that sample 1A has the highest saturation flux density, initialpermeability, and lowest DC energy loss, while sample 2A has the lowestAC power loss. The annealed samples have higher permeability andsaturation flux density and a lower coercivity than their un-annealedcounterparts. Annealing reduces internal stress and dislocation density,and increases grain size, thereby reducing the resistance to movement ofmagnetic domain boundaries. Since samples 1 and 1A correspond to ahigher combustion temperature than samples 2 and 2A they have a higherpercentage of fully melted particles coupled with a lower porosity. As aresult, sample 1A has a higher permeability and lower coercivity thansample 2A. Sample 2A, on the other hand, has lower eddy currents and acorresponding lower AC power loss due to its lower percentage of fullymolten particles.

Since the insulation layers are composed of alumina, which is stable athigh temperatures, heat treatment is very effective in improvingsaturation flux density and permeability as well as in decreasingcoercivity without compromising on the insulation layers and eddycurrent losses. With regard to samples 1A and 2A, these samples havemore desirable magnetic properties than the sample designated as P1 inTable 1.

Further improvements in magnetic properties may be achievable by changesto process parameters as well as particle chemistry and size. Forexample, there may be an optimal set of process parameters that willresult in a combustion temperature that lies in between those of samples1 and 2, leading to a lower percentage of fully melted particles and, atthe same time, keeping the porosity at negligible levels. In addition,the use of powder with larger sized particles may result in lowerhysteresis losses as this will facilitate free movement of magneticdomain boundaries. A reduction in carbon content in the alloy to under0.05% will also result in a significant decrease in carbide impuritiescontributing to lower hysteresis losses. Also, there is likely anoptimal lower percentage of aluminum in the Fe—Al alloy that will resultin an increase in the saturation flux density without compromising theintegrity of the inter-particle insulation.

Example 2

The particle size and shape previously considered was in the range of15-45 microns in size and spherical in shape. Magnetic materials arecomprised of aggregates of magnetic micro-domains which grow in thedirection of the applied magnetic field. When the material is comprisedof aggregates of particles, the presence of insulation layers may limitthe movement of domain boundaries to the particle boundaries, therebylimiting the effective permeability and saturation flux density. Inaddition, simulations of material properties may show that the idealration of particle dimensions to boundary dimensions is 1000:1. Sinceinsulation layers previously obtained had a thickness of 0.1-0.5microns, it is generally desirable for particle sizes to be in the100-200 micron range.

In the thermal spray processes using HVAF and HVOF, particle sizes aretypically in the 15-45 micron range as this size allows the particles toacquire sufficient velocity and temperature to form a dense soliddeposit. In order to spray larger sized particles, certain processmodifications are needed in order to increase the energy and enthalpyinput to the particles.

In order to determine the feasibility of spraying larger sizedparticles, experiments were conducted with a thermal spray powder(Metco-450NS, available from Oerlikon Metco, of Switzerland), which isan alloy of 95% nickel and 5% aluminum of a larger size range of 45-90microns. The thermal energy input to the particles was controlled byselecting the combustion chamber and the mechanical energy input wascontrolled by selecting the right exit diameter of the convergingdiverging nozzle. After some experimentation, a densely packed layer ofthe deposited particles was obtained. FIG. 43 shows the microstructureof the resulting material. The material layers at the bottom weresprayed with a smaller combustion chamber and the layers at the top weresprayed using the larger combustion chamber. The velocity of the exitingparticles was controlled by selecting an appropriate size ofconverging-diverging nozzle.

Although carbon is added to assist in the atomization process, carbondoes not form a solid solution with iron and instead forms carbideprecipitates which obstruct the movement of magnetic domain boundaries,thereby lowering permeability and saturation flux density. Therefore,the carbon was replaced with silicon (which improves magneticpermeability) to enable atomization. At concentrations below 7.5%,silicon formed a solid solution with a BCC lattice structure and hencedid not form precipitates. In addition, at low concentrations, silicondid not inhibit the formation of alumina at the temperatures below 1500C, as indicated in the phase diagrams of FIGS. 44A and 44B, which showan isopleth of Fe-9% Al—Si alloy showing a BCC structure up to 1400degrees C. (FIG. 44A(a)), an isopleth of Fe-9% Al-1% Si—O showingpreference for the formation of alumina (FIG. 44A(b)), an isopleth ofFe-10% Al—C showing a BCC structure up to 1000 degrees C. (FIG. 44B(a)),and an isopleth of Fe-10% Al—O showing preference for the formation ofalumina (FIG. 44B(b)). After such consideration, an alloy composition ofFe-9% Al-1% Si was selected for spray forming tests. The powder with theabove concentration was successfully produced by a gas atomizationprocess, and the concentration of carbon was reduced to 0.04%. Theaddition of silicon reduced the melting point of the alloy marginally.This was expected to be beneficial in the spraying of larger sizedparticles.

The presence of aluminum as an alloying element facilitated theformation of insulation layers. However, it also reduced the saturationflux density of the material. At 10% by weight, the saturation fluxdensity of the alloy was reduced by 20% from that of pure iron. It wasthus determined to be desirable to have a particle chemical compositionthat is satisfies the following conditions:

(a) Sufficient concentration of aluminum at the surface to form acontiguous layer of aluminum oxide at the surface and at the same timehave less or no aluminum beneath the surface in order to ensure a highsaturation flux density; and

(b) The aluminum at the surface should be present in the form of a solidsolution of iron and aluminum rather than elemental aluminum. This isbecause elemental aluminum has a melting point lower than the operatingtemperature of the thermal spray. In addition, un-oxidized elementalaluminum will form an undesirable electrically conducting boundaryaround the particle domains.

Example 3

To obtain approximate performance characteristics of the slotless motor2000, an analytical model was developed and implemented using a computermodelling program. The model was used to obtain a desired set of motorparameters such as number of stator and rotor poles, number of windingturns, and approximate magnet and stator tooth dimensions. Based on themodel, a hybrid field motor conforming to the dimensions in Table 2,with 20 rotor poles, will have a 24% higher motor constant than aconventional motor designed to the same constraints.

TABLE 2 Motor dimensional specification Stator outer diameter 172 mm Airgap (radial)  1 mm Rotor bore diameter 100 mm Motor height (includingend turns)  21 mm

The analytical model, however, has limitations as it does not accountfor nonlinearity in the B—H curve of the soft magnetic material and fluxsaturation. For the same reason, the analytical model is not sufficientto estimate motor constant values for other configurations. In order toobtain a more precise solution, the motors of other configurations wereanalyzed with finite element analysis techniques. As a first step,precise geometric models of the motors have been developed, and thefinite element analysis of the motors was performed.

Optimization criteria in the motor design process included (a)maximization of motor efficiency under static and constant velocityconditions and (b) maximization of torque capacity under constantvelocity operating conditions.

Near-net shape manufacturing was used to form the parts of the motor2000. A thermal process was used to spray ring-shaped parts that wereused to measure magnetic properties per the ASTM A773 standards. Thestrategy used in obtaining the ring-shaped sample was modified to obtainthe stator geometries required to fabricate the slotless and corelessmotor shown in FIG. 33. The stator geometries in the other motorsutilized a strategy that involved the use of masks or stencils and acontrolled movement of the stencil (as shown in FIG. 45) in response tomeasurements of the material deposition depth. This required measurementsystems to measure deposited material thickness and a stencil actuationmechanism that was coordinated with a robot controlling the spraysystem. A computer operated as a master controller that performed thetask of coordination between the measurement systems, the stencilactuation mechanism, and the spray system.

Stencils and masks of complex shapes were employed in the fabrication ofmolds which were achieved through 3-D printing. The 3-D printed moldswere used to fabricate a prototype of a stator. This prototypingcapability facilitated scrutiny of the stator design particularly withregard to processes that utilized thermal spraying techniques.

Referring now to FIGS. 46A through 46C, there is shown an alternateaspect of the motor shown in FIG. 32. In the embodiment shown, the motoris a slotted motor as opposed to a slotless motor shown in FIG. 32.Stator 1906′ may have applicable features similar to stator 1906 and isprovided having poles or teeth where FIG. 46C shows a section view oftooth 2202 and winding 2204 in a view axial with respect to the motor.FIG. 46A shows a section view of tooth 2202 and winding 2204 in a viewtangential with respect to the stator and passing through the center oftooth 2202. FIG. 46B shows a section view of tooth 2202 and winding 2204in a view tangential with respect to the stator and passing offset fromthe center of tooth 2202 and through tooth 2202 and winding 2204. Tooth2202 is shown having face 2206 and ring portion 2208 connected by coreportion 2210. Here, stator 1906′ is constructed such that thecross-section of winding 2204 remains substantially the same and thecross-section of tooth 2202 remains substantially the same along theflux path. Face portion 2206 is shown having conical surfacesinterfacing with the magnet portions of rotor 1902 and opposing surfacesinterfacing with winding 2204. Core portion 2210 extends from faceportion 2206 to ring portion 2208 and forms the structure about whichthe wires of winding 2204 are wound. Here, core portion 2210 may have anon-uniform cross section, for example, as shown in FIGS. 46A and 46Csuch that the cross-section of winding 2204 remains substantially thesame and the cross-section of tooth 2202 remains substantially the samealong the flux path. Ring portion 2208 may have a triangular crosssection as shown and may provide adjoining structure and a flux path foradjoining teeth. Although stator 1906′ was described with respect to thegeometry shown, any suitable geometry may be provided. Stator 1906′ orany other stator as described may be provided with salient windings asshown or alternately with distributed windings. Similarly, any of thestators described may have skewed poles or any suitable geometry poles.Similarly, any of the stators described may be fabricated with anysuitable soft magnetic material, for example as disclosed, or othersuitable material, for example, sintered, machined, laminated, or anysuitable material.

It should be understood that the foregoing description is onlyillustrative. Various alternatives and modifications can be devised bythose skilled in the art. For example, features recited in the variousdependent claims could be combined with each other in any suitablecombination(s). In addition, features from different embodimentsdescribed above could be selectively combined into a new embodiment.Accordingly, the description is intended to embrace all suchalternatives, modifications, and variances which fall within the scopeof the appended claims.

What is claimed is:
 1. A motor, comprising: a stator comprising at leastone core and an outer wall, the outer wall extending in an axialdirection; a coil wound on the at least one core of the stator such thatan edge of the outer wall extending in the axial direction is below,even with, pr extends beyond a surface of the coil facing in the axialdirection and such that the outer wall terminates at an outer edge ofthe coil; a rotor having a rotor pole and being rotatably mountedrelative to the stator; at least one magnet disposed between the rotorand the stator; and a conical air gap between the stator and the atleast one magnet; wherein a separation plane normal to an axis ofrotation extends through the stator and the rotor, and wherein the coil,the at least one magnet, and the conical air gap are together configuredto allow flux flow between the stator and the rotor in athree-dimensional flux pattern such that the flux flow does not crossthe separation plane.
 2. The motor of claim 1, wherein the rotor poleand the stator in conjunction with the at least one magnet directsmagnetic flux between the rotor and the stator in directions that areoutside of a single plane in three dimensions.
 3. The motor of claim 2,wherein the outer wall inhibits the direction of magnetic flux radiallyoutward from the stator beyond the outer wall.
 4. The motor of claim 1,wherein the stator is configured to approximate a cross sectional shapethat defines surfaces corresponding to a cross sectional shape of the atleast one magnet.
 5. The motor of claim 1, wherein the rotor pole isextended in the direction of the stator to produce the conical air gapbetween the stator and the at least one magnet.
 6. The motor of claim 1,wherein the coil is tapered in the radial direction.
 7. The motor ofclaim 1, wherein the at least one core is formed on a surface of thestator to form a slotless stator.
 8. The motor of claim 1, wherein therotor comprises a first rotor portion and a second rotor portion.
 9. Themotor of claim 1, wherein the stator comprises at least a first statorportion and a second stator portion.
 10. The motor of claim 1, whereinsubstantially all of the magnetic flux is directed circumferentiallyalong the edge of the outer wall to adjacent coils.
 11. The motor ofclaim 1, wherein the at least one magnet comprises two magnets, each ofthe two magnets being magnetized in different directions.
 12. The motorof claim 1, wherein the rotor comprises a first rotor half and a secondrotor half, and wherein the motor is configured to operate based onrotation of either the first rotor half or the second rotor half. 13.The motor of claim 1, wherein the at least one core comprises acomposite material defined by iron-containing particles having analumina layer disposed thereon.
 14. A motor, comprising: a slotlessstator comprising at least one core formed of a soft magnetic compositematerial, an outer wall positioned along a circumference of the at leastone core, and coils disposed on the at least one core, the outer wallpositioned along the circumference of the at least one core extending inan axial direction such that an edge of the outer wall is below, evenwith, or extends beyond a surface of the coil facing in the axialdirection and such that the outer wall terminates at an outer edge ofthe coils disposed on the at least one core; a rotor rotatably mountedrelative to the slotless stator; at least one magnet mounted on therotor between the rotor and the slotless stator; and an air gap betweenthe slotless stator and the at least one magnet, the air gap beingconical in cross sectional shape; wherein a separation plane normal toan axis of rotation extends through the slotless stator and the rotor,and wherein the coils, the at least one magnet, and the conical air gapare together configured to allow flux flow between the slotless statorand the rotor in a three-dimensional flux pattern such that the fluxflow does not cross the separation plane.
 15. The motor of claim 14,wherein the soft magnetic composite material comprises particlescontaining at least iron and having insulating outer surfaces comprisingalumina.
 16. The motor of claim 14, wherein the slotless statorcomprises a wall that forms a continuous surface on which the at leastone core is formed.
 17. The motor of claim 14, wherein the soft magneticmaterial comprises about 89 wt. % iron, about 10 wt. % aluminum, andabout 0.25 wt. % carbon.
 18. The motor of claim 17, wherein the softmagnetic material further comprises silicon.
 19. A slotless flux motor,comprising: a stator defined by a continuous surface at which at leastone core is disposed and a winding disposed on the at least one core, anouter wall circumferentially positioned around the at least one core, anedge of the outer wall extending in an axial direction such that theedge of the outer wall is below, even with, or extends beyond a surfaceof the winding facing in the axial direction and such that the outerwall terminates at an outer edge of the winding disposed on the at leastone core; a rotor having a rotor pole and being rotatably mounted in thestator; and at least one magnet mounted between the stator and the rotorpole; wherein a conical air gap is defined between the stator pole andthe at least one magnet, wherein the conical air gap allows flux flowalong radial, axial, and circumferential directions of the motor;wherein a separation plane normal to an axis of rotation extends throughthe stator and the rotor, and wherein the at least one magnet and theconical air gap are together configured to allow flux flow between thestator and the rotor in a three-dimensional flux pattern such that theflux flow does not cross the separation plane; and wherein the at leastone core comprises a soft magnetic composite material defined byiron-containing particles encapsulated in alumina.
 20. The slotless fluxmotor of claim 19, wherein the iron-containing particles comprise aniron-aluminum alloy comprising about 89 wt. % iron, about 10 wt. %aluminum, and about 0.25 wt. % carbon.
 21. The slotless flux motor ofclaim 20, wherein the iron-containing particles further comprisesilicon.
 22. The slotless flux motor of claim 19, wherein theiron-containing particles include one or more of iron-cobalt alloy,iron-nickel alloy, and iron-silicon alloy.
 23. The slotless flux motorof claim 19, wherein the at least one core is self-supported on aninner-facing surface of the stator and has a horizontal V-shaped crosssection.